Improvement in bbidbes



@uitrit tstee identit @ffice JAMES K. THOMPSON, OF CHICAGO, ILLINOIS, ASSI'GNOR TO HIMSELF AND WILLIAM B. HOWARD, OF SAME PLAGE.

Letters Patent No. 81,960, dated September 8, 1868.

IMPROVEMENT IN BRIDGES.

TO ALL ,WHOM IT MAY GONCERN:

Beit known that I, JAMES K. THOMPSON, of the city of Chicago, in' the county of Cook, and.` State of Illinois, have invented' certain new and useful Improvements in Howe Truss-Bridges, and I do hereby declare that thefollowing is a full, clear, and exact description thereof, reference heinghd to the accompanyindicating like parts wherever they occur.

'To enable others skilled in the art to construct and use` my invention, I will proce-edle describe it.

In the accompanying drawingA v Figure 1 nepresents a side elevation, and y Figure 2. a plan of a draw-bridge with myjimprov'ements. The nature of my invention consists in the construction and arrangement of the wrought-iron lower and upper chords, to be used for draw or permanent bridges', in such a manner as to adept them to be readily substituted for the wooden chords of the so-called Howe truss,n and t'o be easily combined with other parts of the said Howe truss, therebyimproving the said truss and making it more durable. i l Each of my chords A A consists of three ormore continuous wrought-iron bars, a a', placed edgewnys, 'and spaced so as `to conform themselves to the width of the bearingsor shoes B B, generallynsed in the Howetruss. y i In draw-bridges,the upper chord may be strengthened in the middle of the bridge by one or m'ore additional bars, a a', as represented ou lig. A2, in which case the central' two or more bars may be drawn into one or two bars'at n. proper distance fromthe centre of the bridge, so as to form the chords toward the ends of the bridge of the same number of bars as there are in thelower chord, or of more, if desirable. l l i In'order to connect the bars 'a a of my chords, and to give a bearing 4to the nuts cl d of the suspension-rods C C, I place wrought-iron plates, b b, under and across the-bars a a of the lower chord,- and plates' b b over and across the bars a a the upper chord, the suspension-rods C C passing through the bearngsB B, and plates'b B" of the chords'are tightened by the nuts d 'el and hold the structure together. v The b'srs a a' of the chords are n also provided with holes for the lateral tension-rods D D to pass through and be tightened und secured by the,

`nuts ff on the outside of the bars of the chords A A'. Y In order to stiifen the chords between the counter-braces P P, iron stays E E are placed over and across-the "l bars a c' of each chord, :und the Vsaid stays and bars are .bolted together.

It isevident from the above4 description, that I substitute for the wooden chords ofthe Howe truss the wrought-iron chords, and construct said chords in such a manner as to adapt them to readily combine with other prtsf theFHowetruss, the, advantage'cf such a combination consisting in the additional strength of the truss, economy of its construction, undl greater durability of the bridge, as the wooden braces can .easilybe removed and renewed from 4time tc time, without any material disturbance to the iron chords. i i

I Whntlclaim as new and my invention, and desire to secure by Letters Patent, is

The wrought'iron chords A A', each yconsisting of everal bars placed apart and edgeways, and the plates.` b b' and stays E, connecting the said bars, when used and Varranged substantially as herein described aud' specified.l

JAMES K. THOMPSON.

'l Witness-es: 1

J. B. TUncniN, N. K. Knosnnn.

ing drawings, making partei' this specification, and tothe letters of referenceA marked thereon, like letters 

